This invention relates to a process for converting brines into useful products, and more particularly to converting saline waters such as oil field brine wastes, seawater, or other inland saline waters into fertilizer, salt, and/or purified process water.
Oil field operations generate waste products in the production and handling of crude oil. These waste products include drilling mut pit waters and oil field brines. The quantities of brines produced in oil fields can be substantial, with brine fractions accounting for from 4 to 96 percent of the total liquid volume produced. Brines from other inland or seawater sources also present disposal problems.
Various methods of disposal of these brines have been attempted including solar evaporation, distillation, controlled release of brines into surface waters, and injection of brines into subterranean formations. However, in areas of high annual rainfall and/or high relative humidity, such as much of the midwestern and eastern portions of the United States, solar evaporation becomes impractical. Moreover, with increasing state and federal regulatory pressures, diversion of large volumes of brine into surface waters is not an environmentally acceptable solution.
While distillation as a means of recovering fresh water from these saline sources has been attempted, the presence in such brines of a large proportion of divalent metal chlorides such as calcium and magnesium chloride have greatly complicated recovery efforts. These metal chlorides are highly corrosive to process equipment surfaces and deposit hard to remove mineral scales. This scale deposition becomes an even greater problem when the brines are heated.
Presently, brine treatment using dissolved air flotation methods to remove suspended oil, followed by deep well injection of the brine is regarded by the United States Environmental Protection Agency as the best practicable technology for disposal. However, deep well injection is expensive, difficult to design to a given level of capacity, and requires careful conditioning of the brine prior to injection. Economies of scale favor deep well injection systems having capacities of millions of gallons of brines per month. However, in oil fields in the midwestern and eastern U.S. where less brine wastes are produced than in western oil fields, and where the oil fields themselves are smaller, deep well injection may not, in many instances, be an economically feasible disposal alternative.
Accordingly, the need exists for a cost effective and environmentally acceptable method for the disposal of oil field waste brines and other saline water sources.